Melanin Inhibitory Effect of Tuber himalayense Isolated in Incheon, Korea.

There has been a growing interest in skin beauty and antimelanogenic products. Melanogenesis is the process of melanin synthesis whereby melanocytes are activated by UV light or hormone stimulation to produce melanin. Melanogenesis is mediated by several enzymes, such as tyrosinase (TYR), microphthalmia-associated transcription factor (MITF), tyrosinase-related protein-1 (TRP-1), and TRP-2. In this study, we investigated the effect of Tuber himalayense extract on melanin synthesis in α-melanocyte-stimulating hormone (α-MSH)-treated B16F10 melanoma cells. We confirmed that T. himalayense extract was not toxic to α-MSH-treated B16F10 melanoma cells and exhibited a significant inhibitory effect on melanin synthesis at concentrations of 25, 50, and 100 µg/ml. Additionally, the T. himalayense extract inhibited melanin, TRP-1, TRP-2, tyrosinase, and MITF, which are enzymes involved in melanin synthesis, in a concentration-dependent manner. Furthermore, T. himalayense extract inhibited the mitogen-activated protein kinase (MAPK) pathways, such as extracellular signal-regulated kinase-1/2 (ERK), c-Jun N-terminal kinase (JNK), and p38. Therefore, we hypothesized that various components of T. himalayense extract affect multiple factors involved in melanogenesis in B16F10 cells. Our results indicate that T. himalayense extract could potentially be used as a new material for preparing whitening cosmetics.

Inhibition of Microsomal Prostaglandin E2 Synthase Reduces Collagen Deposition in Melanoma Tumors and May Improve Immunotherapy Efficacy by Reducing T-cell Exhaustion.

The arachidonic acid pathway participates in immunosuppression in various types of cancer. Our previous observation detailed that microsomal prostaglandin E2 synthase 1 (mPGES-1), an enzyme downstream of cyclooxygenase 2 (COX-2), limited antitumor immunity in melanoma; in addition, genetic depletion of mPGES-1 specifically enhanced immune checkpoint blockade therapy. The current study set out to distinguish the roles of mPGES-1 from those of COX-2 in tumor immunity and determine the potential of mPGES-1 inhibitors for reinforcing immunotherapy in melanoma. Genetic deletion of mPGES-1 showed different profiles of prostaglandin metabolites from that of COX-2 deletion. In our syngeneic mouse model, mPGES-1-deficient cells exhibited similar tumorigenicity to that of COX-2-deficient cells, despite a lower ability to suppress PGE2 synthesis by mPGES-1 depletion, indicating the presence of factors other than PGE2 that are likely to regulate tumor immunity. RNA-sequencing analysis revealed that mPGES-1 depletion reduced the expressions of collagen-related genes, which have been found to be associated with immunosuppressive signatures. In our mouse model, collagen was reduced in mPGES-1-deficient tumors, and phenotypic analysis of tumor-infiltrating lymphocytes indicated that mPGES-1-deficient tumors had fewer TIM3+ exhausted CD8+ T cells compared with COX-2-deficient tumors. CAY10678, an mPGES-1 inhibitor, was equivalent to celecoxib, a selective COX-2 inhibitor, in reinforcing anti-PD-1 treatment. Our study indicates that mPGES-1 inhibitors represent a promising adjuvant for immunotherapies in melanoma by reducing collagen deposition and T-cell exhaustion. Significance: Collagen is a predominant component of the extracellular matrix that may influence the tumor immune microenvironment for cancer progression. We present here that mPGES-1 has specific roles in regulating tumor immunity, associated with several collagen-related genes and propose that pharmacologic inhibition of mPGES-1 may hold therapeutic promise for improving immune checkpoint-based therapies.

Enhancement of TRP Gene Expression and UV Absorption by Bioconverted Chestnut Inner Shell Extracts Using Lactiplantibacillus plantarum.

In this work, the suppression of tyrosinase-related genes, including an improvement in UV absorption effects of bioconverted CS extracts (BCS), was investigated to improve the skin-whitening effect. Total polyphenols and total flavonoids, which are bioactive components, increased 2.6- and 5.4-times in bioconversion using Lactiplantibacillus plantarum SM4, respectively, as compared to ultrasound-assisted extracts (UCS). The effect of BCS on radical scavenging activity, UV-A absorption, and tyrosinase activity inhibition, contributing to skin-whitening, were 1.3-, 1.2-, and 1.2-times higher than those of UCS, respectively. The main component identified in high-performance liquid chromatography (HPLC) was gallic acid in both UCS and BCS, which increased by 2.9-times following bioconversion. The gene expression of tyrosinase-related proteins, including TRP-1 and TRP-2 genes, was studied to confirm the suppression of melanin synthesis by BCS in order to identify the skin-whitening mechanism, and BCS decreased both genes' expression by 1.7- and 1.6-times, demonstrating that BCS effectively suppressed melanin synthesis. These findings imply that the chestnut inner shell can be employed as a cosmetic material by simultaneously inhibiting melanogenesis and enhancing UV-A absorption through bioconversion using L. plantarum SM4.

Cajanin Suppresses Melanin Synthesis through Modulating MITF in Human Melanin-Producing Cells.

Despite its classification as a non-life-threatening disease, increased skin pigmentation adversely affects quality of life and leads to loss of self-confidence. Until now, there are no recommended remedies with high efficacy and human safety for hyperpigmentation. This study aimed to investigate anti-melanogenic activity and underlying mechanism of cajanin, an isoflavonoid extracted from Dalbergia parviflora Roxb. (Leguminosae) in human melanin-producing cells. Culture with 50 µM cajanin for 48-72 h significantly suppressed proliferation in human melanoma MNT1 cells assessed via MTT viability assay. Interestingly, cajanin also efficiently diminished melanin content in MNT1 cells with the half maximum inhibitory concentration (IC50) at 77.47 ± 9.28 µM. Instead of direct inactivating enzymatic function of human tyrosinase, down-regulated mRNA and protein expression levels of MITF and downstream melanogenic enzymes, including tyrosinase, TRP-1 and Dct (TRP-2) were observed in MNT1 cells treated with 50 µM cajanin for 24-72 h. Correspondingly, treatment with cajanin modulated the signaling pathway of CREB and ERK which both regulate MITF expression level. Targeted suppression on MITF-related proteins in human melanin-producing cells strengthens the potential development of cajanin as an effective treatment for human hyperpigmented disorders.

Salicylic acid in ginseng root alleviates skin hyperpigmentation disorders by inhibiting melanogenesis and melanosome transport.

Abnormal melanogenesis and melanosome transport can cause skin pigmentation disorders that are often treated using ginseng-based formulation. We previously found that phenolic acid compounds in ginseng root could inhibit melanin production and as a skin-whitening agents. However, mechanisms of action underlying effects of ginseng phenolic acid monomers on melanogenesis remain unclear. This study was conducted to investigate effects of salicylic acid, a main ginseng root phenolic acid component, on melanogenesis and melanosome functions in melanocytes of zebrafish and other species. Salicylic acid exhibited no cytotoxicity and reduced melanin levels and tyrosinase activity in B16F10 murine melanoma cells and normal human epidermal melanocytes regardless of prior cell stimulation with α-melanocyte stimulating hormone. Additionally, salicylic acid treatment reduced expression of melanogenic enzymes tyrosinase, tyrosinase-related protein 1 and tyrosinase-related protein 2, while reducing expression of their master transcriptional regulator, microphthalmia-associated transcription factor. Moreover, reduced phosphorylation of cAMP response-element binding protein was observed due to reduced cAMP levels resulting from salicylic acid inhibition of upstream signal regulators (adenylyl cyclase and protein kinase A). Furthermore, salicylic acid treatment suppressed expression of transport complex-associated proteins melanophilin and myosin Va in two UVB-treated melanocytic cell lines, suppressed phagocytosis of fluorescent microspheres by UVB-stimulated human keratinocytes (HaCaT), inhibited protease-activated receptor 2 activation by reducing both Ca2+ release and activation of phosphoinositide 3 kinase/AKT and mitogen-activated protein kinases and induced anti-melanogenic effects in zebrafish. Collectively, these results indicate that salicylic acid within ginseng root can inhibit melanocyte melanogenesis and melanin transport, while also suppressing keratinocyte phagocytic function.

Jasmonic Acid Plays a Pivotal Role in Pollen Development and Fertility Regulation in Different Types of P(T)GMS Rice Lines.

Two-line hybrid rice systems represent a new technical approach to utilizing the advantages of rice hybrids. However, the mechanism underlying the male sterile-line fertility transition in rice remains unclear. Peiai 64S (PA64S) is a photoperiod- and thermo-sensitive genic male sterile (PTGMS) line in which male sterility manifests at an average temperature above 23.5 °C under long-day (LD) conditions. Nongken 58S (NK58S) is a LD-sensitive genic male sterile (PGMS) rice that is sterile under LD conditions (above 13.75 h-day). In contrast, D52S is a short-day (SD)-PGMS line that manifests male sterility under SD conditions (below 13.5 h-day). In this study, we obtained fertile and sterile plants from all three lines and performed transcriptome analyses on the anthers of the plants. Gene ontology (GO) analysis suggested that the differentially expressed genes identified were significantly enriched in common terms involved in the response to jasmonic acid (JA) and in JA biosynthesis. On the basis of the biochemical and molecular validation of dynamic, tissue-specific changes in JA, indole-3-acetic acid (IAA) levels, gibberellin (GA) levels, and JA biosynthetic enzyme activities and expression, we proposed that JA could play a pivotal role in viable pollen production through its initial upregulation, constant fluctuation and leaf-spikelet signaling under certain fertility-inducing conditions. Furthermore, we also sprayed methyl jasmonate (MEJA) and salicylhydroxamic acid (SHAM) on the plants, thereby achieving fertility reversal in the PGMS lines NK58S and D52S, with 12.91-63.53% pollen fertility changes. Through qPCR and enzyme activity analyses, we identified two key enzymes-allene oxide synthase (AOS) and allene oxide cyclase (AOC)-that were produced and upregulated by 20-500-fold in PGMS in response to spraying; the activities of these enzymes reversed pollen fertility by influencing the JA biosynthetic pathway. These results provide a new understanding of hormone interactions and networks in male-sterile rice based on the role of JA that will help us to better understand the potential regulatory mechanisms of fertility development in rice in the future.

Engineering 'Enzymelink' for screening lead compounds to inhibit mPGES-1 while maintaining prostacyclin synthase activity.

Aim: This study investigated our Enzymelinks, COX-2-10aa-mPGES-1 and COX-2-10aa-PGIS, as cellular cross-screening targets for quick identification of lead compounds to inhibit inflammatory PGE2 biosynthesis while maintaining prostacyclin synthesis. Methods: We integrated virtual and wet cross-screening using Enzymelinks to rapidly identify lead compounds from a large compound library. Results: From 380,000 compounds virtually cross-screened with the Enzymelinks, 1576 compounds were identified and used for wet cross-screening using HEK293 cells that overexpressed individual Enzymelinks as targets. The top 15 lead compounds that inhibited mPGES-1 activity were identified. The top compound that specifically inhibited inflammatory PGE2 biosynthesis alone without affecting COX-2 coupled to PGI2 synthase (PGIS) for PGI2 biosynthesis was obtained. Conclusion: Enzymelink technology could advance cyclooxygenase pathway-targeted drug discovery to a significant degree.

Evaluation of the effect of narrow band-ultraviolet B on the expression of tyrosinase, TYRP-1, and TYRP-2 mRNA in vitiligo skin and their correlations with clinical improvement: A retrospective study.

Narrowband-ultraviolet B (NB-UVB) is considered one of the main therapeutic tools in vitiligo, which is able to induce repigmentation and halt depigmentation. However, little remains known about the effect of NB-UVB on TYR gene family, the main pigmentary genes, in vitiligo patients. To assess the effect of NB-UVB on expression of some genes related to the pigmentary problem of vitiligo; tyrosinase (TYR), tyrosinase related protein 1 (TYRP1) and tyrosinase related protein 2 (TYRP2), mRNA levels of those genes were quantitatively evaluated by Real-Time quantitative Polymerase Chain Reaction (RT-qPCR) in skin biopsies obtained from 30 patients with nonsegmental vitiligo and five healthy controls. Vitiligo patients were classified into two groups; group 1, involving 12 untreated vitiligo patients and group 2, including 18 vitiligo patients treated by NB-UVB. The levels of TYR, TYRP-1, and TYRP-2 mRNAs in untreated group were significantly lower than in control subjects (P < .001). In NB-UVB treated group, the three genes were significantly higher than in group 1 (P < .001), however, they were still significantly lower than in the control subjects (P < .001). A significant positive correlation was detected between TYR and TYRP-2 genes in group 2 (P = .03). This study demonstrated that mRNA level of TYR, TYRP-1, and TYRP-2, which decreased in vitiligo, was significantly increased upon treatment with NB-UVB. Accordingly, the mechanism of depigmentation in vitiligo disease and repigmentation by NB-UVB treatment may be related to the changes in the expression of these genes.

Novel bisthiolane polysulfides from lachrymatory factor synthase-suppressed onion and their in vitro cyclooxygenase-1 inhibitory activity.

Two novel bisthiolane polysulfides (compounds 1 and 2), trivially named thiolanotrisulfide and thiolanotetrasulfide, were isolated from a reaction model of tearless onion (in which lachrymatory factor synthase is suppressed), and the presence of another novel bisthiolane polysulfide (3), trivially named thiolanopentasulfide, was confirmed. On the basis of spectroscopic and mass spectrometric analyses, it was found that these bisthiolane polysulfides were bis(5-hydroxy-3,4-dimethylthiolan-2-yl)-tri/tetra/pentasulfide with the general formulas of C12H22O2S5 (tri-), C12H22O2S6 (tetra-) and C12H22O2S7 (penta-), and they were confirmed to exist in authentic tearless onion juice. Thiolanotrisulfide (1) and thiolanotetrasulfide (2) inhibited cyclooxygenase-1 activity with IC50 values of 720 ± 78 and 464 ± 48 µM respectively, compared with 3282 ± 188 µM for aspirin.

Designed CXCR4 mimic acts as a soluble chemokine receptor that blocks atherogenic inflammation by agonist-specific targeting.

Targeting a specific chemokine/receptor axis in atherosclerosis remains challenging. Soluble receptor-based strategies are not established for chemokine receptors due to their discontinuous architecture. Macrophage migration-inhibitory factor (MIF) is an atypical chemokine that promotes atherosclerosis through CXC-motif chemokine receptor-4 (CXCR4). However, CXCR4/CXCL12 interactions also mediate atheroprotection. Here, we show that constrained 31-residue-peptides ('msR4Ms') designed to mimic the CXCR4-binding site to MIF, selectively bind MIF with nanomolar affinity and block MIF/CXCR4 without affecting CXCL12/CXCR4. We identify msR4M-L1, which blocks MIF- but not CXCL12-elicited CXCR4 vascular cell activities. Its potency compares well with established MIF inhibitors, whereas msR4M-L1 does not interfere with cardioprotective MIF/CD74 signaling. In vivo-administered msR4M-L1 enriches in atherosclerotic plaques, blocks arterial leukocyte adhesion, and inhibits atherosclerosis and inflammation in hyperlipidemic Apoe-/- mice in vivo. Finally, msR4M-L1 binds to MIF in plaques from human carotid-endarterectomy specimens. Together, we establish an engineered GPCR-ectodomain-based mimicry principle that differentiates between disease-exacerbating and -protective pathways and chemokine-selectively interferes with atherosclerosis.

Astragalus Polysaccharide (PG2) Suppresses Macrophage Migration Inhibitory Factor and Aggressiveness of Lung Adenocarcinoma Cells.

Astragalus membranaceus is the most popular traditional Chinese medicine for managing vital energy deficiency. Its injectable polysaccharide PG2 has been used for relieving cancer-related fatigue, and PG2 has immune-modulatory and anti-inflammatory effects. In this study, we explored the effects of PG2 in lung adenocarcinoma A549 and CL1-2 cells and investigated its anticancer activity, and the results were validated in severe combined immunodeficiency (SCID) mice. Although PG2 did not inhibit the growth of these cells, it dose-dependently suppressed their migration and invasion, accompanied by reduced vimentin and AXL and induced epithelial cadherin (E-cadherin) expression. Regarding the underlying molecular mechanism, PG2 treatment reduced the macrophage migration inhibitory factor (MIF), an inflammatory cytokine that promotes the epithelial-mesenchymal transition and aggressiveness of cancer cells. Consistent with the previous finding that MIF regulates matrix metalloproteinase-13 (MMP-13) and AMP-activated protein kinase (AMPK), treatment with PG2 reduced MMP-13 and activated AMPK in A549 and CL1-2 cells in this study. In SCID mice injected with A549 cells through the tail vein, intraperitoneal injection with PG2 reduced lung and abdominal metastases in parallel with decreased immunohistochemical staining of AXL, vimentin, MMP-13, and MIF in the tumor. Collectively, data revealed a potential application of PG2 in integrative cancer treatment through the suppression of MIF in cancer cells and their aggressiveness.

Thymocid®, a Standardized Black Cumin (Nigella sativa) Seed Extract, Modulates Collagen Cross-Linking, Collagenase and Elastase Activities, and Melanogenesis in Murine B16F10 Melanoma Cells.

Black cumin (Nigella sativa) seed extract has been shown to improve dermatological conditions, yet its beneficial effects for skin are not fully elucidated. Herein, Thymocid®, a chemically standardized black cumin seed extract, was investigated for its cosmeceutical potential including anti-aging properties associated with modulation of glycation, collagen cross-linking, and collagenase and elastase activities, as well as antimelanogenic effect in murine melanoma B16F10 cells. Thymocid® (50, 100, and 300 µg/mL) inhibited the formation of advanced glycation end-products (by 16.7-70.7%), collagen cross-linking (by 45.1-93.3%), collagenase activity (by 10.4-92.4%), and elastases activities (type I and III by 25.3-75.4% and 36.0-91.1%, respectively). In addition, Thymocid® (2.5-20 µg/mL) decreased melanin content in B16F10 cells by 42.5-61.6% and reduced cellular tyrosinase activity by 20.9% (at 20 µg/mL). Furthermore, Thymocid® (20 µg/mL for 72 h) markedly suppressed the mRNA expression levels of melanogenesis-related genes including microphthalmia-associated transcription factor (MITF), tyrosinase-related protein 1 (TYRP1), and TYRP2 to 78.9%, 0.3%, and 0.2%, respectively. Thymocid® (10 µg/mL) also suppressed the protein expression levels of MITF (by 15.2%) and TYRP1 (by 97.7%). Findings from this study support the anti-aging and antimelanogenic potential of Thymocid® as a bioactive cosmeceutical ingredient for skin care products.

7,8-Dimethoxycoumarin stimulates melanogenesis via MAPKs mediated MITF upregulation.

Background: Melanin in the skin is the defense against the harmful UV radiation, which is considered as one of the major risk factors for skin cancer. The compound 7,8-dimethoxycoumarin (DMC, C11H10O4), a natural coumarin molecule present in several medicinal plants, possesses antioxidant and anti-inflammatory activities. However, the mechanism underlying its effects on melanogenesis in melanocytes is unclear. Therefore, we investigated the effect of DMC on melanogenesis activation in B16F10 melanoma cells. Methods: We examined the cytotoxic range of DMC on B16F10 melanoma cells and increased effects of melanogenesis, and intracellular tyrosinase activity. In addition, regulation mechanisms were assessed by Western blot analysis. Results: The results showed that DMC significantly increased melanin content and tyrosinase activity in the cells without being cytotoxic. Furthermore, DMC stimulated the expression of tyrosinase, TRP-1, TRP-2, and MITF thereby activating melanin production and Akt phosphorylation was increased in the Akt signaling pathway. on the contrary, interfering with the phosphorylation of ERK in the MAPKs pathway. Conclusions: These results suggest that DMC may serve as a candidate for potential melanin-producing activator and anti-gray hair applications.

Reversing UVB-induced photoaging with Hibiscus sabdariffa calyx aqueous extract.

BACKGROUND: Hibiscus sabdariffa is commonly used in daily life and its extract is applied widely in food and cosmetics. However, it has not been evaluated for its anti-aging effects. RESULTS: Hibiscus sabdariffa calyx aqueous extract (HSCAE) has shown potential collagenase activity suppression effects, together with tyrosinase activity inhibition, and anti-oxidation as a free radical scavenger. The current investigation demonstrated that HSCAE was not cytotoxic in skin fibroblasts, and it significantly decreased ultraviolet B (UVB)-induced reactive oxygen species (ROS) on a flow cytometry assay. Moreover, HSCAE reduced matrix metalloproteinase (MMP) expression, increased tissue inhibition of metalloproteinase (TIMP)-1 level, and enhanced collagen content by inhibiting collagenase activity. It also blocked mRNA and protein expressions of melanin production pathway key factors, including the microphthalmia-associated transcription factor (MITF), tyrosinase, tyrosinase-related protein-1 (TRP-1), and dopachrome tautomerase-2 (TRP-2). CONCLUSION: These results demonstrated, for the first time, the potential of HSCAE as a natural antioxidant with the ability to maintain collagen production and to decrease melanin syntheses under UVB radiation, for anti-aging effects. © 2019 Society of Chemical Industry.

ER-depletion lowering the 'hypothalamus-uterus-kidney' axis functions by perturbing the renal ERß/Ptgds signalling pathway.

Researchers have long assumed that systematic estrogen fading might contribute to the sustained progression of menopausal degenerate syndromes, although definitive evidence has not been presented. Whether such findings represent a causal contribution or are the result of opportunistic messengers sent from the reproductive system to the brain is also a vital question. We constructed a multiscale network of the ovariectomy (OVX) induced estrogen receptors depletion (ER-depletion) model and integrated targeted proteomic, targeted lipidomic, cytochemical, and histopathological data across three tissues from the ovariectomy rodent model. We found that compared to control rats, OVX rats showed increased renal and uterine prostaglandin D2 synthase (Ptgds) expression and decreased hypothalamic Ptgds expression, abnormal Ptgds metabolites, the degenerate renal function profiles and decreased cognitive ability (learning and memory) in Morris water maze test. Importantly, we observed a regulatory relationship among ER (particularly ERß), the degree of the pathological phenotype, learning behavior test and the 'hypothalamus-uterus-kidney (HUK) axis functions. Collectively, this study elucidates that ER depletion promoted HUK aging is mostly attributed to a renal ERß/Ptgds signalling imbalance.

Gynostemma pentaphyllum saponins induce melanogenesis and activate cAMP/PKA and Wnt/ß-catenin signaling pathways.

BACKGROUND: Melanogenesis is a physiological process of melanin production in response to UV exposure, which is modulated through multi-signaling pathways including cAMP/PKA, Wnt/ß-catenin and MAPK signaling cascades. HYPOTHESIS/PURPOSE: The present study aims to investigate the molecular mechanism of hyperpigmentation induced by Gynostemma pentaphyllum saponins. STUDY DESIGN/METHODS: In this study, we investigated the melanogenic effects of triterpenoid saponins of Gynostemma pentaphyllum (GpS), a medicinal plant. Two mouse melanogenic cell lines B16 and B16F10 were employed for the current study. RESULTS: The results showed that non-toxic doses of GpS markedly increased melanin formation in both B16 and B16F10 cells. Western blot analysis showed that GpS treatment significantly up-regulated the expression levels of the key melanogenic proteins, including tyrosinase (TYR), microphthalmia-associated transcription factor (MITF), TRP-1 and TRP-2 in a dose-dependent manner. The phospho-CREB, which is the downstream target of PKA is also elevated upon GpS treatment. We further observed that H89, a PKA inhibitor, attenuated the GpS induced tyrosinase activity, melanin content, the expression of phospho-CREB. In addition to the cAMP/PKA signaling pathway, GpS treatment also up-regulated the ß-catenin of the Wnt signaling pathway which is involved in the transcriptional activation of MITF in melanogensis. We further demonstrated that treatment with GpS markedly enhance mRNA expression of MITF, along with the downstream target molecules, TYR, TRP-1 and TRP-2. Knock-down MITF with siMITF inhibited the expression of MITF mRNA by 63%, and the melanin content was reduced 70% in the siMITF-transfected cells compared to untransfected or scramble siRNA control cells. CONCLUSION: These findings demonstrated strong melanogenic activities of GpS, and the MITF is essential for the melanogenesis stimulated by GpS.

Vanillic acid in Panax ginseng root extract inhibits melanogenesis in B16F10 cells via inhibition of the NO/PKG signaling pathway.

Panax ginseng C. A. Meyer has been widely used in skin care. Our previous study showed that the phenolic acids in ginseng root extract (GRE) impart inhibitory effects on melanogenesis. In this study, we found that as the most abundant component of phenolic acids in GRE, vanillic acid decreased tyrosinase activity and melanin levels with or without α-MSH stimulation and suppressed the expression of microphthalmia-associated transcription factor (MITF) and melanogenic enzymes in B16F10 cells. Furthermore, vanillic acid downregulated NOS activity, nitric oxide (NO) content, cGMP level, guanylate cyclase (GC) and protein kinase G (PKG) activity, and the phosphorylation of cAMP-response element-binding protein (CREB), whereas arbutin had no effect on the NO/PKG pathway. These findings indicate that vanillic acid in GRE suppressed melanogenesis by inhibiting the NO/PKG signaling pathways. This study provides a potential mechanism underlying the inhibitory effect of ginseng on melanogenesis.

Protopanaxatriol inhibits melanin synthesis through inactivation of the pCREB-MITF-tyrosinase signalling pathway in melanocytes.

Ginsenosides are major active components of ginseng, and have diverse pharmacological properties in traditional medicine. Recent reports have shown that ginsenosides modify skin physiology and mitigate skin disorders such as photoageing and hyperpigmentation. We evaluated the antimelanogenic efficacy of protopanaxatriol, a major category of ginsenosides, as a depigmenting agent. Protopanaxatriol significantly reduced intracellular and extracellular melanin content in a concentration-dependent manner in B16 melanoma cells treated with α-melanocyte-stimulating hormone. In normal human epidermal melanocytes, protopanaxatriol clearly decreased melanin synthesis and dendrite elongation. In addition, protopanaxatriol dramatically suppressed the expression of genes encoding the melanogenic proteins tyrosinase, tyrosinase-related protein-1 and -2, and microphthalmia-associated transcription factor through dephosphorylation of cAMP response element-binding protein. These results suggest that protopanaxatriol could be an effective candidate anti-melanogenic agent.

The Inhibition of Melanogenesis Via the PKA and ERK Signaling Pathways by Chlamydomonas reinhardtii Extract in B16F10 Melanoma Cells and Artificial Human Skin Equivalents.

Abnormal melanin synthesis results in several hyperpigmentary disorders such as freckles, melanoderma, age spots, and other related conditions. In this study, we investigated the antimelanogenic effects of an extract from the microalgae Chlamydomonas reinhardtii (CE) and potential mechanisms responsible for its inhibitory effect in B16F10, normal human epidermal melanocyte cells, and human skin-equivalent models. The CE extract showed significant dose-dependent inhibitory effects on α-melanocyte-stimulating, hormone-induced melanin synthesis in cells. Additionally, the CE extract exhibited suppressive effects on the mRNA and protein expression of microphthalmia-associated transcription factor, tyrosinase, tyrosinase-related protein-1, and tyrosinase-related protein-2. The CE extract also inhibited the phosphorylation of protein kinase A and extracellular signal-related kinase, which function as upstream regulators of melanogenesis. Using a three-dimensional, reconstructed pigmented epidermis model, the CE-mediated, anti-pigmentation effects were confirmed by Fontana-Masson staining and melanin content assays. Taken together, CE extract can be used as an anti-pigmentation agent.